1. Field of Invention
The invention relates to a method for printing a test pattern used to inspect a printing element which forms dots on a recording medium, to an image forming device forming a test pattern on a recording medium by the method, and to a recording medium on which a test pattern is formed by the image forming device.
2. Description of Related Art
Image forming devices, such as inkjet printers, for forming an image on a fed recording medium are widely used. As disclosed in Japanese Laid-Open Patent Publication No. 9-94950 (1997), some image forming devices are known to print a test pattern, which is a regular-shaped image, on a recording medium. The test pattern is used to check whether each printing element works correctly.
Image forming devices of this type are provided with a plurality of printing elements, a print head mounting the printing elements thereon, moving means for moving the print head above a recording medium, and control means for controlling the printing elements, the print head, and the moving means. The control means controls each element such that each element ejects droplets of ink for a predetermined period, during the time when the moving means moves the print head. The image forming device thus prints a test pattern composed of a single line printed by each printing element. Because a clogged printing element does not eject an ink droplet and therefore does not print a line, a user can judge whether each printing element is clogged, by observing the test pattern visually, or by reading the test pattern with an image-reading device, such as a scanner. The condition of each printing element is thus checked.
However, because the test pattern printed by the image forming device of this type is composed of a very thin single line, each being a sequence of droplets of ink ejected by each printing element, an automatic judgment by an image-reading device, such as a scanner, sometimes fails. Especially, when brightness of the test pattern is high, even the visual observation takes a long time to make the judgment. As the size of the printing element gets smaller, this problem becomes even more significant.